Rectum Flashcards Preview

How long is the rectum

15cm

What vertebral level does the rectosigmoid junction occur at

S3

Describe peritoneal covering of the rectum

First third - peritoneum over anterior and lateral surfaces Middle third - peritoneum over anterior surfaceLast third - subperitoneal

4

What happens to smooth muscle at the rectosigmoid junction

Teniae coli of the sigmoid colon spread to form a continuous outer longitudinal layer of smooth muscle

5

What are the major flexures of the rectum

SacralAnorectal

6

What is the sacral flexure

Anteroposterior curve following the curve of the sacrum and coccyx, therefore it is concave anteriorly

7

What is the anorectal flexure

Anteroposterior curve that is concave posteriorly

8

What forms the anorectal flexure

Tone of the puborectalis muscle

9

Function of the anorectal flexure

Contributes significantly to faecal continence (ability to control bowel movements)

10

What are the lateral flexures of the rectum

SuperiorIntermediateInferior

11

What forms the lateral flexures

Transverse folds of the internal rectal wall

12

What is the distal segment of the rectum

Ampulla

13

Function of the ampulla of the rectum

It relaxes to accumulate and temporarily store faeces until defecation occurs

14

What's directly anterior to the rectum in males and females

Males - rectovesical pouchFemales - rectouterine pouch

15

Link embryological origins to the blood supply of the rectum

The proximal rectum is derived from the hindgut and so its blood supply is via the inferior mesenteric artery The distal rectum receives its blood supply from branches off the internal iliac arteries

16

Arterial supply of the proximal rectum

Aorta -> IMA -> right and left superior rectal arteries

17

Arterial supply of the distal rectum

Aorta -> common iliac -> right and left internal iliac -> right and left middle rectal arteries Aorta -> common iliac -> right and left internal iliac -> inferior pudendal -> right and left inferior rectal arteries

18

Venous drainage of the rectum

Superior, middle and inferior rectal veins

19

What does the superior rectal vein drain into

IMV, splenic vein then the hepatic portal vein

20

What do the middle and inferior rectal veins drain into

Systemic venous system

21

Site of the portocaval anastomosis (where do the portal and systemic venous systems anastomose)What is the significance of this

Wall of the anal canal Clinically important in varices (portal hypertension)